The present invention relates to energy storage devices, and, in particular, relates to capacitors and, more particularly, to supercapacitors.
It is a known fact that the capacitance is proportional to the plate area and inversely proportional to the distance the plates are apart in a parallel plate capacitor, for example; the energy density is proportional to the capacitance and inversely proportional to the volume between the plates. Thus in order to make a supercapacitor one would attempt to increase the capacitance and decrease the volume between the plates. The use of dielectric material further enhances the above characteristics.
In the past, the need for stored energy was provided by capacitor banks which proved to be bulky and more prone to failure. In applications having a need to minimize the amount of space used for energy storage, there is a need for a supercapacitor.
High energy density capacitors have high surface area electrodes and ion-mobile electrolyte instead of typical capacitor plates and dielectric. The electrode material is characterized by a fine microporous texture which is responsible for its high surface area and must be filled with electrolyte in order to gain access to a large portion of the available area.
With regard to capacitor construction, solid electrolyte has advantages over liquid electrolyte. But from a functional standpoint, use of liquid electrolyte is more straightforward. Liquid electrolytes are generally nonviscous at room temperature and readily wet the electrode surface. With liquid electrolyte, gaining access to the total electrode surface is often no major problem. However, a more elaborate set of procedures is required if solid electrolyte is to be used. An electrode impregnation process must be employed for effective utilization of the total surface area, yet the process must not have adverse effects upon electrolyte quality.